Portions of the vasculature of a patient may be treated to restore adequate blood flow in an occluded blood vessel. Conditions for which blood-flow restoration may be indicated include atherosclerosis and other conditions that may cause narrowing of a lumen of a blood vessel. In some examples, a system for restoring adequate blood flow may include an expandable balloon positioned on a catheter and received within a sheath. During treatment, a clinician may advance the balloon through the sheath and into the vasculature of the patient, navigate the balloon to a treatment site within a target vessel, and then expand the balloon to restore patency of the target vessel. Some balloon sheaths may be configured to be longitudinally split into two portions to enable a clinician to remove the sheath from the catheter once the balloon has been advanced through the sheath. In some examples, expandable balloons may include a drug coating to help prevent re-stenosis of the target vessel.